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The Diff: NBA conference imbalance and the East playoffs

The Diff is your weekly Wednesday WFNY look into the amazing world of sports statistics. For a complete log of articles, click this link. Last week, I had a rare hiatus. Two weeks ago, I wrote about fun Cleveland Cavs facts that we keep forgetting. Now, it’s more NBA playoffs talk.

When we talk about the Cleveland Cavaliers in 2013-14, it’s important to note their improvements in the context of the bourgeoning NBA Eastern Conference. Not only are the Cavs expected to improve, but so are several other teams. The Toronto Raptors, Washington Wizards, Detroit Pistons and others all could claim that they are the franchise most expected to take a leap in the downtrodden East. But before anyone can do so, it’s necessary, from a statistical perspective, to describe what historically has been the expectation for a playoff team in the NBA’s lesser conference. The numbers tell a fascinating tale.

The clearest place to start is with the birth of the Charlotte Bobcats franchise for the beginning of the 2004-05 season. Since then, the NBA has featured two even 15-team conferences, each including three five-team divisions. Then, from each conference, there are eight playoff teams. While the playoffs have featured various orders of seeding structure over the years, it’s always been the case that the best eight teams, as shown by record, in each conference make the playoffs. That’s what matters for this study.

The usual NBA season features 82 games for each team. Of those games, 52 are within the conference – with 16 against the other four teams in their respective division – and 30 are against the other conference. Of course, this was not the case in the 66-game lockout-shortened season from 2011-12. That year, 48 games were within the conference for each team, a far larger proportion than usual.

The best place to begin is showing the respective conference strengths. The general NBA narrative over the last decade would clearly state how the Western Conference has featured the more dominant franchises. While they’ve only won five of the last nine championships, their playoffs have generally featured more 50-plus win teams. And the West has dominated inter-conference play. Here’s the breakdown:

(Because of the lockout-shortened year, I averaged the nine seasons’ winning percentages together to achieve the final average. That’s the formula I’ll use later on as well.)

On average, over this data set, the West-East relations equates to the West team winning at the pace of a 46-win NBA team. Only one year, and just slightly, has the East won the majority of inter-conference games. Most years have played out like the last three: With the West dominating, especially in terms of more 50-win teams and a more competitive playoff atmosphere.

What does that mean in reality? Clearly, it’s easier to be a team in the East. That fits within the general NBA narrative, and especially for the 2013-14 season. While there are five known playoff teams in the East – Miami, Indiana, Brooklyn, Chicago and New York, in some order – again the West has a plethora of long-time and up-and-coming contenders vying for just eight playoff nods. It is possible that nine teams in the West will be better than the East’s No. 6 seed.

And that’s actually been the case on average over these past nine years. Here’s the next charting, averaging out winning percentages by conference rank1

There’s the money chart. The difference between the two conferences represents a bottleneck shape; the imbalance is most striking in the middle range, from the No. 4-10 seed, while it’s not as notable at the ends, especially at the very top. The East has featured some incredible dominant regular season teams in this stretch – i.e. any team with LeBron James – creating a huge difference between the No. 1 and No. 2 seed. That provides for the small margin.

Then, in the middle ranges, the average NBA season in terms of conference playoff structure has played out very similarly to what we might expect here in 2013-14. The East featured just a handful of actually good teams – with maybe five this season compared to usually three – while the West was loaded. The most striking examples were in 2008 (Denver) and 2010 (Portland/San Antonio/Oklahoma City), when the West’s No. 8 seed actually had 50 wins, a hallmark of a really impressive season.

Previously, I wrote in The Diff about usual jumps that 24-win NBA teams make. In that setting and with no other context, I pegged the Cavaliers to make the jump to being a 30-32 win team for the 2012-13 season. That’s just the historical expectation for those bad teams as they continued their regression to the mean. The biggest point from that article was that NBA teams are historically .500 over time, so that’s the usual long-term potential of any really, really bad season.

But the 2013-14 Cavaliers are not a team that we should analyze in a vacuum. Their success – as measured by wins on the court – is a factor of the relative strength of the Eastern Conference and how they stand up next to the other middle-tiered teams. As I shared before, Toronto, Washington, Detroit and other fans all have similar aspirations for the season to at least compete for a playoff spot, and not really contend just yet for the cherished NBA title.

So how exactly has the East’s middle tier looked in terms of win distribution over the last nine seasons? Let’s take a look at each year:

Now one can actual see the usual success of a No. 5-10 seed in the East.2 And nothing ever has approached the 50-win beacon I was just describing that has occurred twice in nine years at the No. 8 playoff spot in the West. In fact, in four out of these nine years, the East playoffs have featured a team with a sub-.500 record, another hallmark for mediocrity and not-really-belonging-in-the-playoffs-ness.

So when people talk about the Eastern Conference playoff order for this coming season, context is needed. The average No. 5 seed in the East only has won 44.6 games over the past nine years, when using winning percentage as a guide. For the No. 6 seed, that’s 42.9 wins. For the No. 7 seed, 41.9. For the No. 8 seed, 39.7. For the No. 9 seed, 37.2. For the No. 10 seed, 34.1.

Removing the vacuum from before, it’s likely that that pattern will continue going forward. For the Cavaliers, Raptors, Wizards and Pistons, etc., it shows that the goal should be competing for the 40-44 win category. That, usually, has been enough for a middle-tier team in the East to nab a playoff spot. And it’s because those teams are so mediocre in the NBA context when it comes to competing against the Western Conference 30 times out of an 82-game schedule.

Do I think the Cavaliers are good enough to be considered a lock for the playoffs in 2013-14? Absolutely not. They’re in the same mix as those other teams with the hope to make a fairly large leap this coming season. For any leap, a combination of internal improvement, long-term health and, yes, some luck is needed when it comes to actually being a .500-ish team over the duration of 82 games.

But do I think the Cavs have a nice shot to be a 40-44 win team that struggles against the top-tier teams of the East, can’t usually find sustainable success against two-thirds of the West and somehow scrambles into the playoffs like the other mediocre East teams over the last near-decade? For sure. That’s the context and frame of mind fans should have with respect to this season. These numbers show how it’s not pretty, but mediocrity is all it takes to move forward just a little bit.

As I said before, specific playoff seeding has taken on a multitude of variations over the years. I simply sorted by wins in each conference to come up with these “ranks”. It’s not an exact science, but the best and easiest mathematical work I could do. [↩]

Obviously, for the lockout-shortened 2011-12 season, that win number is estimated based on their winning percentage for the 66 games. But it was necessary to frame everything in the context of an 82-game season. [↩]

Jacob Rosen is a long-time contributor to WaitingForNextYear. He's also a writer online at SportsAnalyticsBlog and Nylon Calculus . An Akron native, Jacob is a current MBA student at the University of Oregon's Warsaw Sports Marketing Center. You can follow him on Twitter @WFNYJacob or e-mail him at udjrosen(at)gmail(dot)com.